A brake system for actuating a pair of front wheel brakes and a pair of rear wheel brakes is selectively operable during a manual push-through mode. A primary power transmission unit actuates at least one of wheel brakes in a normal braking mode. A secondary power transmission unit actuates the front wheel brakes in a backup braking mode. A primary electronic control unit controls at least one of the primary power transmission unit and a pair of rear brake motors. A secondary electronic control unit controls at least one of the secondary power transmission unit and the rear brake motors. An ABS modulator arrangement is hydraulically interposed between at least one of first and second three-way valves and at least a selected wheel brake. A multiplex control valve arrangement is hydraulically interposed between the secondary power transmission unit and the front wheel brakes.